1. Field of the Invention
The invention relates to a radiant heater, particularly for use in heating glass ceramic hotplates, baking-roasting equipment, etc., as well as to a method and apparatus for the production thereof.
2. Prior Art
The fixing of heating coils to insulators for radiant heaters takes place either by insertion in grooves of the insulator, by fixing with clips to the insulator surface or by embedding the heating coil in a moist insulator, into which the coil is pressed and fixed there after drying. The latter method has proved very advantageous, but is relatively complicated and mainly requires fibrous insulating material, which has a good mechanical strength, but has lower thermal insulation characteristics. Therefore an aerosil layer is normally placed under the insulator and which, whilst having good thermal stability and excellent electrical and thermal insulation characteristics, has a lower mechanical strength.
It is also known to so shape the heating coils at individual points that projections are formed, which are pressed round by the insulator during the production thereof (EP-A-71 048).
Previous attempts to embed heating coils or projections directly into such an aerosil have failed. If it was wished to use such a material, then fixing would have to take place by means of clips or shaped out projections of the heating coils.